Postsurgical Temporary Epicardial Pacing: Electrophysiological Implications of Contemporary Pacing Lead Designs

Despite advancements in postoperative temporary epicardial pacing leads, sensing malfunction can still happen. Oversensing presents as inappropriate inhibition of pacing (a major concern for pacemaker-dependent patients), whereas undersensing may lead to an extremely rare complication of ventricular fibrillation from R on T. The single-lead and dual-lead configurations have key structural differences related to the size of the bipole electrodes and the spacing between them. We assessed how this affects the sensing function.

Five porcine studies were conducted using open chest and Langendorff models. We used 2 pacing wire configurations and compared the sensed electrograms. We compared a newer single-lead configuration (small, closely spaced electrodes) with a dual-lead (large, widely spaced) configuration. The primary outcome was the amplitude of the R wave. Secondary outcomes were the relative size of the T wave and the effect of sampling frequency and low-pass filtering.

The sensed QRS was significantly larger in the widely spaced, larger electrodes when compared with closely spaced, smaller electrodes across all sampling frequencies and filter settings (6.9-29.7 mV vs 1.7-8.6 mV, P < 0.001). The average amplitude of the T wave was closer to the average QRS amplitude with the newer configuration across all settings. The mean T wave to R wave difference ranged from 3.0 to 3.7 mV for the single lead and 1.0 to 21.5 mV for the dual lead configuration. Large, widely spaced electrodes resulted in much larger sensed QRS signals and a safer programming window for sensitivity.

The smaller, closely spaced electrodes detect a relatively small QRS and a larger T wave, leading to a narrower safety window and an increased risk of sensing malfunction (Central Illustration). To avert catastrophic consequences, the electrophysiologic implications of new temporary pacing wires must be considered during postoperative care.